1. Field of the Invention
This invention relates to polyphenylene ether/polyamide blend compositions which exhibit improved dimensional stability and high-temperature capability.
2. Description of the Prior Art
Polyphenylene ether (PPE) polymers are thermoplastic polymers exhibiting various superior properties, including mechanical properties, heat resistance, electrical properties, chemical resistance and flame resistance. However, PPE polymers suffer from inferior processability due to their high melt viscosity and have a tendency to crosslink at the high processing temperature needed for melt flow. Polyamides, commonly known as nylon resins, are well known for possessing an outstanding combination of strength, toughness and chemical resistance as well as for their processability, but conventional polyamides are hygroscopic and, thus, are not dimensionally stable. Consequently, it is desirable to produce PPE/polyamide blend compositions in which useful properties of the two polymers are maintained. However, as is known in the art, PPE and polyamides are not compatible and when blended together, they do not form a composition of practical use since the polymers have significantly different melt viscosities and polarities.
Various methods of improving compatibility of PPE polymers and polyamides are disclosed in the prior art, which include U.S. Pat. No. 4,315,086 to Ueno et al., U.S. Pat. No. 4,600,741 to Aycock et al., U.S. Pat. No. 4,732,938 to Grant et al., and U.S. Pat. No. 4,863,996 to Nakazima et al. Although these prior art disclosures provide compatibilized PPE/polyamide blends having improved impact properties and processability, these compositions still do not provide dimensional stability and high-temperature capability.
U.S. Pat. No. 4,990,564 to Taubitz et al. discloses a PPE/polyamide blend that is heat distortion resistant and mold-shrink resistant. The blend contains a copolyamide that is composed of 20-90% by weight of units derived from terephthalic acid and hexamethylenediamine, and at least 10% of aliphatic polyamide units, either of nylon 6 or nylon 6,6 units. Although the blend disclosed therein exhibits improved properties including heat distortion resistance, the blend retains the moisture sensitivity and dimensional instability against heat and moisture of conventional polyamides.
It therefore would be desirable to provide PPE/polyamide compositions that exhibit high dimensional stability and high-temperature capability as well as improved impact properties and processability over the prior art PPE/polyamide compositions.